Réponse :
Bonjour
Explications étape par étape
Notons a,b, c et d les 4 chiffres recherches
nous pouvons ecrire 4 equations
(1) a + b = 8
(2) a + c = 13
(3) c - d = 6
(4) b + d = 8
(2) - (1) donne
a + c - a - b = 13 - 8
(1') c - b = 5
(3) + (4) donne
c - d + b + d = 14
(2') b + c = 14
(1') + (2') donne
c - b + b + c = 14 + 5 = 19
2c = 19
c = 19/2 = 9.5
de (2') b = 14 - 19/2 = (28-19)/2 = 9/2 = 4.5
de (1) a = 8 - 9/2 = (16-9)/2 = 7/2 = 3.5
de (3) d = 19/2 - 6 = (19-12)/2 = 7/2 = 3.5
donc
a = 3.5
b = 4.5
c = 9.5
d = 3.5
